linux-kernel - Re: [stable 5.10 v2 PATCH 1/2] mm: hwpoison: remove the unnecessary THP check

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Date:   Mon, 8 Nov 2021 09:06:44 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Yang Shi <shy828301@...il.com>
Cc:     naoya.horiguchi@....com, hughd@...gle.com,
        kirill.shutemov@...ux.intel.com, willy@...radead.org,
        osalvador@...e.de, peterx@...hat.com, akpm@...ux-foundation.org,
        stable@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [stable 5.10 v2 PATCH 1/2] mm: hwpoison: remove the unnecessary
 THP check

On Thu, Nov 04, 2021 at 02:07:51PM -0700, Yang Shi wrote:
> commit c7cb42e94473aafe553c0f2a3d8ca904599399ed upstream.
> 
> When handling THP hwpoison checked if the THP is in allocation or free
> stage since hwpoison may mistreat it as hugetlb page.  After commit
> 415c64c1453a ("mm/memory-failure: split thp earlier in memory error
> handling") the problem has been fixed, so this check is no longer
> needed.  Remove it.  The side effect of the removal is hwpoison may
> report unsplit THP instead of unknown error for shmem THP.  It seems not
> like a big deal.
> 
> The following patch "mm: filemap: check if THP has hwpoisoned subpage
> for PMD page fault" depends on this, which fixes shmem THP with
> hwpoisoned subpage(s) are mapped PMD wrongly.  So this patch needs to be
> backported to -stable as well.
> 
> Link: https://lkml.kernel.org/r/20211020210755.23964-2-shy828301@gmail.com
> Signed-off-by: Yang Shi <shy828301@...il.com>
> Suggested-by: Naoya Horiguchi <naoya.horiguchi@....com>
> Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Peter Xu <peterx@...hat.com>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> ---
>  mm/memory-failure.c | 14 --------------
>  1 file changed, 14 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 01445ddff58d..bd2cd4dd59b6 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -956,20 +956,6 @@ static int get_hwpoison_page(struct page *page)
>  {
>  	struct page *head = compound_head(page);
>  
> -	if (!PageHuge(head) && PageTransHuge(head)) {
> -		/*
> -		 * Non anonymous thp exists only in allocation/free time. We
> -		 * can't handle such a case correctly, so let's give it up.
> -		 * This should be better than triggering BUG_ON when kernel
> -		 * tries to touch the "partially handled" page.
> -		 */
> -		if (!PageAnon(head)) {
> -			pr_err("Memory failure: %#lx: non anonymous thp\n",
> -				page_to_pfn(page));
> -			return 0;
> -		}
> -	}
> -
>  	if (get_page_unless_zero(head)) {
>  		if (head == compound_head(page))
>  			return 1;
> -- 
> 2.26.2
> 

Thanks, both now queued up.

greg k-h